1. Field of Invention
The present invention relates to a rotary plug valve that not only can be opened to fluid flow or closed to fluid flow but can also be selectively and securely locked-closed to fluid flow. In limited application, an adaptation can make this concept lock-open to fluid flow.
2. Description of the Prior Art
Since the inception of piping distribution systems and gas systems in particular, it has been necessary to control the opening and closing of gas supply to each location as required and to securely lock the gas supply for safety and to secure property. Externally exposed locks, shields, shrouds, wings, and locking apertures have been easily sawed, hammered, pried, broken, sheared, levered and otherwise tampered with to circumvent the locking security. Internal locking mechanisms have been complicated, such as spring activated plungers, magnets, single operation mechanisms, and mechanisms requiring special tools that may not be available in emergency situations where fire, police, or emergency may have need to secure an installion.
An unauthorized turn-on of a gas supply can create a fire, explosion or suffocation at some point downstream of the gas valve, particularly in new projects, in renovations, and in unoccupied buildings. In such locations all appliances may not be completely installed. Branch lines may be temporarily not inspected. Unauthorized turn-on of the gas supply can be disasterous.
In cases of non-payment of past due bills, unauthorized turn-on of the gas supply is theft.
U.S. Pat. No. 3,560,130, issued Jan. 15, 1968 to this inventor, created a simple and effective internal locking device, whereby the valve housing enshrouded a locking pin such as a gas-industry-utilized Smith-Morse or E.J. Brooks "Barrel" lock. The vulnerable exposed wings were made internal and an internally concealed locking cap secured a standard locking pin. The locking pin that passed through a cavity through the valve housing, through the valve core and locked into the blind locking cap. To create this internally concealed passageway, additional material was added to two sides of the valve housing, creating two protrusions.
After over twenty years of usage throughout the United States, millions of valves installed, and thousands of valves attacked, some shortcomings to this device became known. Where headroom or sideroom was limited, necessary access for installing the locking pin may have presented some difficulty Access to installing was limited to a single plane at right angles to the inlet and outlet piping. The extra material needed to create the internal locking pin passageway presented some installation difficulty, but, most significantly, these protrusions gave some indication as to where the valve could possibly be attacked. Although there are no reported cases of gas being stolen because of a failed (after thousands of attempts) valve, the many mutilated valves had to be replaced at some cost. Since the valve was designed to fail-safe, hazards were not created. Determining that an unauthorized gas turn-on had been attempted was generally easy, but efforts to determine who was responsible were not as successful.
Some manufacturers of the valves had had problems registering the locking pin through its passageways in the valve core and valve body when the core migrated due to wear on the valve seat. In an attempt to facilitate lining up the holes, those of skill in the art made all the lock pin holes larger, which made the pin more vulnerable to an attack by a puller.